Field of the Invention
The present invention relates to a method of detecting and analyzing light including sunlight. More particularly, the present invention relates to a method of showing differences in photons in electric signals in accordance with the condition and characteristic of the atmosphere using sunlight traveling through the atmosphere and adjusting light quantity such that the quantity of incident light is maintained uniform. The present invention makes it possible to considerably improve observation accuracy by making it possible to adjust observation equipment within a short time in sensitive response to a change in light quantity. Further, the present invention relates to an apparatus for detecting photons according to an atmospheric condition, using a function of adjusting light quantity that can significantly improve reliability of an atmospheric condition analysis result by minimizing noise in a spectrum by maintaining light quantity uniform within a predetermined range regardless of atmospheric conditions and changes, and to a method of adjusting light quantity.
Description of the Related Art
Observing the atmosphere can be considered as a typical way of detecting and analyzing photons in the atmosphere and an FTS (Fourier Transform Spectrometer) can be considered as a typical analysis device for observing the atmosphere.
An FTS receives sunlight through the atmosphere and then divides the sunlight traveling through the atmosphere, using an interferometer such as a Fabry-perot interferometer and a Michelson interferometer. The FTS, thereafter, produces an interference pattern by recombining the divided sunlight rays to generate optical path differences that form the interference pattern. The interference pattern is detected by an optical detection system in the FTS and is transformed into an absorption spectrum showing wavelength absorbance at each frequency by Fourier transform. The absorption spectrum has mechanism information relating to interactions between light and substances, depending on differences in peak width, depth, and gap. Accordingly, the FTS makes it possible to observe distribution of substances absorbing corresponding frequencies in the atmosphere by detecting whether specific frequency components are absorbed, by detecting and then analyzing light in the atmosphere.
Further, the FTS includes an optical sensor as a photoelectric transformer that transforms sunlight into electric signals.
In the related art, as examples of the FTS described above, there are Korean Patent Application Publication No. 10-2000-0015251 (Patent Document 1), titled “light path difference generator using two couples of flat mirrors for Michelson interferometer for Fourier transformed spectroscopy and Japanese Patent No. 3038810 (Patent Document 2), titled “observation spectrometer”. Further, as examples of the optical sensor that transforms sunlight into electric signals in the FTS, there are a ultraviolet LED as an optical sensor in a ultraviolet index measuring apparatus disclosed in Korean Patent No. 10-1465694 (Patent Document 3) and a optic sensor for an automobile that makes it possible to control temperature and light in accordance with areas in a vehicle depending on the direction of sunlight by detecting sunlight using two optical diodes disclosed in Korean Patent No. 10-0587479 (Patent Document 4).
The FTSs and optical sensors in the related art are used to detect characteristics of the atmosphere by transforming an optical signal of an interference pattern detected by photoelectric transformation, producing a spectrum by dividing the transformed electric signal for each wavelength through Fourier transform, and then analyzing the spectrum.
However, the devices of Patent Documents 1 and 2 are used to detect characteristics of the atmosphere by producing an interference pattern by interfering with incident light with an optical interferometer, transforming the optical signal of the interference pattern detected through optical transformation, and dividing the electric signal for each wavelength through Fourier transform. That is, since the devices do not transform incident light directly into an electric signal, but transform light into an electric signal by producing an optical interference pattern and the perform Fourier transform, an interferometer is needed and the configuration of a light receiving unit is complicated.
Further, the optical sensors disclosed in Patent Document 3 and 4 sense light using an LED, so they can provide a technique capable of blocking diffused light except for light to be observed, and accordingly, efficiency of light sensing and accuracy in analysis result are low.
Further, since the light quantity depends on the incident direction of light to be observed such as sunlight, measurement signal values of light in the atmosphere are variable, so accurate measurement is impossible. That is, the quantity of sunlight traveling into the FTSs or the photoelectron conduction tip depends on the condition of the atmosphere or the time of measurement. Even if the quantity of sunlight is in a variable range, that is, a predetermined range, when intensive light temporarily travels into the FTSs or when light rapidly appears in accordance with the conditions of the atmosphere, the FTSs cannot temporarily read the intensity value of sunlight. This phenomenon deteriorates reliability of observed data by acting as noise in a spectrum.
In the related art, there is a device called a cam that measures light quantity in an FTS. The cam sets an area, shows sun intensity by marking dots, which indicate how much light travels in the area, and then showing the distribution of the dots. Accordingly, it is possible to obtain information about sun intensity in real time, but it is impossible to adjust a difference in sun intensity.
Further, in the related art, there U.S. Patent Application Publication No. 2010-0039641 (Patent Document 5, published on 18 Feb., 2010), which discloses ‘a micro-ring spectrometer having an adjustable opening’ that makes it possible to adjust light quantity by selecting a frequency using an adjusting plate of which the focal distance can be adjusted, but it also cannot provide a technique making light quantity uniform in accordance with time and conditions of the atmosphere and a configuration for improving measurement reliability of an FTS.